Chinese investors who were prepared to spend at least £1bn (€1.16bn) on Nama's Northern Ireland assets hoped the agency's then Northern Ireland adviser could secure Irish or UK passports for them as part of the deal.

Chinese investors who were prepared to spend at least £1bn (€1.16bn) on Nama's Northern Ireland assets hoped the agency's then Northern Ireland adviser could secure Irish or UK passports for them as part of the deal.

The request was contained in an email that an English businessman representing the investors sent to Frank Cushnahan in November 2011.

In the email, the businessman said he had already told the potential investors he was "pretty sure" they could secure "permanent resident status" either here or in the UK. But he added that this would be "up to the politicians to see if it could be arranged".

He described the investors as being "severely wealthy".

It is understood Mr Cushnahan assured the English businessman in February 2012 that he was progressing the possibility of securing entrance visas for what he termed the "main Chinese investors".

Mr Cushnahan allegedly told the English businessman that he had approached an individual with significant political connections to assist with the preparation of the potential investors' applications for entrance visas.

A spokesman for Mr Cushnahan said he had no comment to make "on these or other selective communications relating to legitimate business discussions, which he was satisfied had been bona fide and lawful".

Mr Cushnahan remains at the centre of the ongoing controversy surrounding Nama's sale of its Northern Ireland loan book to US private equity giant Cerberus in April 2014 for €1.6bn.